Sports cards worth, as a search, is almost always asked about a box rather than a card, and a box does not have a price. What it has is a handful of cards that might. The route from one to the other is a sort followed by a small number of careful readings, and it is the same in every sport.
Accept that most of it is bulk
Collections assembled for enjoyment are mostly base cards from high-production years, and those are worth what postage costs. This is not a disappointing accident; it is what the print runs imply. Treating the bulk as bulk from the start is what frees the time to read the few cards properly.
Sort on what is printed, not on who is pictured
Serial numbers, manufacturer autographs, game-used wording, anything that is not a base card, and anything dated before about 1980. Those five criteria do the sorting in every sport. Names do not, because a famous player on a common card is a common card.
Price the short list from completed sales
Five recent sales of the exact card in your condition, with the highest and lowest dropped. That figure is defensible to a buyer because it is built from what buyers paid. The checker on this site does the arithmetic and shows you the spread so you know how solid it is.
Then decide what you are actually doing
Selling individually maximises the total and costs the most time, because every card is a listing, a message and a package. Selling the lot is faster and cheaper and yields less. Knowing the value of the top twenty is what lets you make that trade deliberately instead of by default.
Questions people ask about sports cards worth
Can a dealer value my collection for free?
Dealers offer to buy, which is a different thing from a valuation, and this site does not direct readers to businesses. Pricing your best twenty cards first means you can evaluate any offer.
Is it worth selling common cards at all?
Individually, rarely: the fee and postage take most of a low price and the time takes the rest. In bulk, sometimes, and that is how most of a collection moves.
Do I need to grade before selling?
Only where the arithmetic says so, which is a minority of cards. The cost and uplift calculators answer it per card.
What about tax on a large sale?
Gains on collectibles have their own treatment in the United States and it is worth reading before a large sale rather than after it.